1. Field of the Invention
This invention relates to improved piston assemblies for various uses and for replacement of conventional hydraulic cylinders, one embodiment having a central velocity tube which passes through the piston head for providing hydraulic thrust to the inside of the piston rod during the downstroke.
2. Description of the Prior Art and Objects of the Invention
Various piston assemblies including pneumatic and hydraulic types have been utilized in the past for a variety of purposes including baling, compacting and pressing and other industrial uses. Compacting devices utilizing hydraulic cylinders have been conceived and operated for many years and these devices generally have a single conventional work force piston which can be either pneumatically or hydraulically operated depending upon the quantity of force required as generated by the cylinders. The pistons within the cylinders are sized according to the power sources utilized such as pumps for various hydraulic fluids or pressurized air sources for pneumatic or gas operated cylinders.
Hydraulic device such as presses are well known in the industry and are operated in accordance with Pascal's Principle that: a large force exerted through a short distance is obtained by exerting a small force through a relatively long distance.
In certain standard hydraulic presses, only one work piston is utilized and a single fluid is generally used to power the apparatus and drive the work piston. In certain applications it would be more economically beneficial to have a work piston driven by pneumatic means under certain conditions and under other conditions, to drive the work piston by hydraulic means. It would be more economically feasible to power a piston under relatively low power or pressure until the work load is reached, and upon contact with the work load, a higher power or pressure provided to actually perform the work such as stamping, compacting or the like. In addition it would be advantageous to move the piston at a greater velocity under a no load condition, and upon reaching the work load the piston could then decrease its speed while increasing it power.
However, conventional hydraulic and pneumatic cylinders generally utilize a single pump or power source to drive the piston under a single, constant power or pressure and much energy is wasted by the cylinder prior to the work being reached by the relatively slow piston speed.
Therefore, with the shortcomings and disadvantages known to prior art hydraulic and pneumatic piston assemblies the present invention was conceived and one of its objectives is to provide a piston assembly having dual power and method of operation which is more economical and efficient to operate than conventional piston assemblies.
It is another objective of the present invention to provide a piston assembly and method whereby a piston assembly can be operated utilizing one or more means such as pneumatic or hydraulic to drive the piston.
It is another objective for this invention to provide a piston assembly which can be used to retrofit existing pneumatic and hydraulic equipment, which will use a smaller, more economical power supply.
It is yet another objective of the present invention to provide a method of operating a piston assembly whereby fluid under relatively low pressure is directed into the piston assembly housing to rapidly move a piston head to the work load and whereafter means are then employed to supply a relatively high pressure or force to further drive the piston to create the force necessary for the particular work load.
It is likewise an objective of the invention to provide an embodiment of the piston assembly having a hollow piston rod which is in fluid communication with a central velocity tube which passes through the piston head whereby, when fluid is pumped into the hollow piston rod causing the piston to advance, fluid is drawn into the piston well by means of atmospheric pressure filling the void created by the vacuum force.
Still another objective of the invention is to provide a piston assembly which will operate with increased cycle speeds due to a two stage fluid input.
Various other objectives and advantages of the present invention will become apparent to those more skilled in the art as a more detailed description of the invention is presented below.